Normal faulting in the forearc of the Hellenic subduction margin: Paleoearthquake history and kinematics of the Spili Fault, Crete, Greece

摘要

The late-Cenozoic kinematic and late-Pleistocene paleoearthquake history of the Spili Fault is examined using slip-vector measurements and in situ cosmogenic (~(36)Cl) dating, respectively. The Spili Fault appears to have undergone at least three successive but distinct phases of extension since Messinian (～7 Ma), with the most recent faulting resulting in the exhumation of its carbonate plane for a fault-length of ～20 km. Earthquake-slip and age data show that the lower 9 m of the Spili Fault plane were exhumed during the last ～16,500 years through a minimum of five large-magnitude (Mw ＞ 6) earthquakes. The timing between successive paleoearthquakes varied by more than one order of magnitude (from 800 to 9000 years), suggesting a highly variable earthquake recurrence interval during late Pleistocene (CV = 1). This variability resulted to significant fluctuations in the displacement rate of the Spili Fault, with the millennium rate (3.5 mm/yr) being about six times faster than its late-Pleistocene rate (0.6 mm/yr). The observed variability in the slip-size of the paleoearthquakes is, however, significantly smaller (CV = 0.3). These data collectively suggest that the Spili Fault is one of the fastest moving faults in the forearc of the Hellenic subduction margin.